Sub-windows within Unity window don't display correctly; anyone know the fix?

There's "void" space between the tabbed windows within the unity main window, where whatever's behind the main window shows through. The small icons in the upper right of each window can't be clicked on. I have to click on a point in the void space to their right to make them function. I can't grab the tabbed window edges where they are displayed, I have to grab a location in the void space to the right of the displayed edge. I have changed the screen resolution; no help. I have rebooted; no help. This is Unity 4.3.2f1. No other apps exhibit this behavior. Win7 home premium, SP1.